High-frequency alternator



Ce t. 18, 1927.

' 1,645,517 J. BETHENOD ETAL v I HIGH FREQUENCY ALTERNATOR Filed Aug. 29, 1921 gum/box J BETHEN00 w EGIRHRDERU gg nwrau Patented Oct. 18, 1927. p I

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JOSEPH BETHENOD EMILE GIRARDEAU, F PARIS, FRANCE. 2 I

rr en-rnnounncy ALTERNATOR.

A lication, filed August 29,1321, Serial n6. 496,553, and in France July 9, 1919 (GRANTED UNDER THE rnovrsrons or runner or Manor: s, 1921, 41 smnr iei'sa I It is the object of the present invention to improve the shap ng of the profile of the teeth of a high frequency alternator. My invention is illustrated'in the tWo figures of 5 the accompanying drawing, in which Flg. 1 represents one arrangement accord ing to my lnventlon, and

quency of the Fig. 2 represents a modification thereoff The present invention is an improvement on the high frequency alternator described in the application of Bethenod and Girardeau, Serial No. 496,552, filed August 29, 1921. That application describes a high frequency alternator, either of the variable impedance or homopolar'type, having a determined harmonic of its fundamental wave accentuated at the expense ofthe fundamental.

In this manner machine is determined by the the output frefrequency of thechosen harmonic insteadof the frequency of the fundamentahthereby increasing considerably the output frequency of the machine.

accordance with the formula d= which a equals the width of This is accomplished by dimensioning the rotor and stator teeth in 2 q rotor and stator teeth, p is the stator pitch and q is the order of the chosen. harmonic.

It is explained that. by thusdimensioning. and spacing the stator and rotor teeth .the amplitude of the chosen harmoni 'willbe very much greater than ,the amplitude of the fundamental any desirable means l wave. By filtering out the fundamental by the frequency of the harmonic can beused astheoutput ghequency of the. machine.

It is further erplalned that by" forming a composite machine consisting of .a single stator anda composite rotor consist ng of a single drum on whlch Were mounted .teeth fora plurality of rotors, several rotors be ng so x]; phase displacement 1n the .teeth 0f the spaced as. to make a their respective outputs equal to A in which as before represents, the order of the chosenharmonic,

the amplitude of the chosen harmonic. Will composite machine.

chosen in pr c e is The harmonic usually that of the third order and obviously a machine designed for this harmonic frequency would necessarily have three rotor teeth. to one stator tooth in the" case of the variable impedance type, and

three rotor teeth to two stator teeth in'the case of thehomopolar type. It, is essential that the W dth of the stator and\the jrotbr' -teeth at theair gapbe equal to eachother,

from r i tfollows t e slots Oaths; stator would be considerably w erthanlth stator teeth. The present invention concerns a redimensioning of the stator teeth so that the eflici'e'ncy of the machine Will be Foucault currents and hysteresis. has been found that in electrical ma; chines comprislng an lnductive winding in .the notches, the maximum efliciency offthe increased by decreasing the losses due .to

machine isattainedwhen the Width of the a;

copper in the notch plus the thickness of the insulator is' equal to the Width of the iron plus t he insulator.- Inthe particular case of'high frequency machines, this condition prevails to a greaterextent becausetheelefcr tromotive force passes" rapidly: through fa maximum; in proportion tolthe differences in the fluxes passing "in two successive notches of thel s'tationary member, thetooth of the stationary inember opposite atooth of "the U:

rotary member being saturated.

-The above "mentioned dimensions hold good ,for a machine inwhich the iron losses due to the reaction fluxare not taken into consideration. If such losses are taken into consideration, the best dimensions are obtained with copper of evenlesser thiekne'ss than iron (b a), theflosses, even heh the inachinefis' under load, being almost entirely inithe iron. a I

,Rel rr new to Fig. 1 of the which, Way of example, illustrates a high frequency alternator of the homopolar type,

designed to, increase the amplitude] of the thirdharmonic at .the' expense of thea'mpli;

tude of 'the yfundamental Wave, S represents the statorfand Rlrep-resents the rotor; 1P represents the stator pole pitch a'nd P Qthe the rotor pole pitch, and as indicated infthe figure,}the ratio of rotor teeth to stator teeth is 3 to 2. notches between stator teeth, is represented byfb; the thickness of the insulation by 6, an-cl thewvidth of the stator teeth by a; In

The width of the copper in the order to' increase 7 the amplitude of the harmonic of a composite machine of this 7 type, it is necessary that the teeth of the rotor comprise three distinct sets of teeth forming, in effect, three separate rotors all co-acting witha single set of teeth on the stator. In the homopolar machine, moreover, it is necessary that there be two stator teeth to each three rotor teeth. As the width of'the rotor and stator teeth must be same at the air-gap, and as the width of the rotor teeth andslots are made equal in practice, it is obvious that such an arrangement would result in a stator having slots considerably wider than its teeth. But as explained above it has been found that in order to. obtain the best efliciency for a machine as Well as to conserve material, the

stator slots should be approximately equal in width to the stator teeth. This efficiency is obtainedby sloping the side faces of the stator teeth, thereby causing them to increase in width a short distance from the air-gap.

The inclination of the side faces of the teeth is, so chosen that throughout the greater e'x'tentof their, length the stator teeth are approximately equal in width to the stator slots as can be clearly seen from Fig. 1 of the is notasdesirable as the preferredform shownin Fig. -1, it is much more desirable than the form shown in the previous application.

It will be seen that by means of this arrangement, the average width of the tooth issuch as to correspond to the best distribution of the losses, between iron-and cop per, and thus correspond to the best utilization of the machine. The particular advantages attained by such arrangement of theeteeth are; a decrease of losses by Fou- V caultcurrents and hysteresis; an increase of the maximum ordinate of the unloaded characteristic of the machine, and finally a decreaseof losses due to the reaction flux.

, The arrangement of the teeth forming the object of the present "invention may be generally applied tov machines having rotatingvpoles irrespective of the method of starting employed, such as ordinary homopolar'machines, or machines with internal starting.

While the invention has been explained by way of example as appliedto a homopolar' machine it is obvious that it average widthat least, as

will be applied equally well to a machine of the variable impedance type.

Having described our invention, what we claim is A 1. In a high frequency alternator, a rotating member slotted at the periphery to form teeth thereon and a stator member slotted to form teeth thereon, said stator having a lesser number of teeth than the rotor and said stator teeth having a winding interposed therebetween and having a width at least as great as the width of the windings thereon] and the teeth of both members having the same width at the air gap. i

2. In ahighfrequency alternator, a slotted rotating pole member having teeth and slots of substantially the same width, a slotted stator member having windings in the slots and having less teeth than the said rotor, the width of said stator teeth being greater than the width of said rotor teeth, and said stator teeth having sides inclined to provide an end of slllibstantially'the same width asthe rotor teet 3. A high frequency alternator compris ing a rotor member and a stator member, each slotted to form teeth thereon, one of said members having a winding interposed between its-teeth and having a smaller number of teeth than the other member, the

teeth of both members having the same width at the air gap and the teethof the winding carrying member having an average width at least as great as the width of the winding between adjacent teeth.

4. A high frequency alternator comprising a rotor member and a stator member, each slotted to form a plurality of teeth, the number of teeth on said members being different and the ratio ofthe number of teeth on the two being not greater than 2: 3 the width of the teeth on both members being equal at their outer extremities and those on the member having the smaller number be ing of a'varying cross section to make their great as the width of the intervening slots.

5. A high frequency alternator compris- I ing a toothed rotor member and a-toothed stator member, one of said members being provided with windingsin slots intermediate said teeth and having a smaller number. of teeth than the other member,'the teeth-of both members having the same width at the air gap and the teeth on the winding carrying member having a. varying cross section to make their maximum width at least as in the slots. p

6. In a high frequencyalternator,a stator and a rotor, a plurality of teeth on said stator and an unequal and greater number of teeth on said rotor co-acting therewith, the

width of teeth on said rotor being equal to the width of the intervening slots, the width great as themaximum width of the windings of the stator teeth at the air-gap being equal to the width of the rotor teeth and the sides of said stator teeth being inclined to make the average width of the stator teeth at least as great as the width of the stator slots.

7. In a high frequency alternator, a stator and, a rotor, a plurality of teeth on said stator and an unequal and greater number of teeth on said rotor co-acting therewith, the width of teeth on said rotor being equal to the width of the intervening slots, the width of the stator teeth at the air-gap being equal to the width of the rotor teeth and the width of the stator teeth at their base being alt least asgreat as the width of the stator s ots.

8. A high frequency alternator comprising a stator, teeth on said stator so spaced as to fornr slots substantially equal in width to the width of said teeth, a winding in said slots, a composite rotor comprising an unequal and greater number of teeth than on said stator, said rotor teeth being so spaced as to make the slots equal in width to the width of the teeth, said stator teeth being bevelled to make their width at the air-gap equal to the Width of the rotor teeth.

7 JOSEPH 'BETHENOD.

EMILE GIRARDEAU. 

